The present invention relates generally to the field of automatic focusing systems and more particularly to the field of automatic focusing systems driven by scene information.
In the prior art there exist automatic focusing systems driven by active range finding devices such as sonar, radar, and laser range finders. Such systems give the subject of the focusing a ready means for detecting that it is under observation. Further, such systems require additional devices and components which increase the burdens of weight, size and power consumption while decreasing overall system reliability. The range information is used to compute where the lens should be while the additional devices and components are required to indicate where the lens actually is and to move it to where computations indicate it should be.
Also in the prior art there exists automatic focusing servomechanism systems that continuously keep a scene in focus. However the continuous fine tuning of these devices are relatively hard wearing on the focusing mechanisms and require upgraded components in these areas. If in order to save power, reduce wear and tear, or reduce the annoyance of continuous fine tuning, the focusing system is pulsed or manually shut off, then there exists the possibility (if not probability) that the object under focus may move out of focus during the off period.
Therefore it is an object of the present invention to provide a non emitting automatic focusing system.
It is another object of the present invention to provide an automatic focusing system which is driven by scene information.
It is yet another object of the present invention to provide an automatic focusing system which is driven by scene information only regardless of the cause of the defocus, be it range variation, thermal expansion or compression of the lens securing structure, variation of the index of refraction with temperature, or any other cause.
It is still yet another object of the present invention to provide a demand auto focus system which is driven by scene information to activate focusing mechanisms only when the image has moved out of focus.